1. Field of the Invention
This invention relates generally to an apparatus and method for bending and forming sheet material such as sheet metal, plate steel and the like. More particularly, the present invention relates to a method and apparatus for enhancing the capability of the lower dies used in press brakes in which performance of multiple forming operations with different gauges of sheet material can be achieved without the need of changing to completely different lower dies. Specifically, the apparatus for bending and forming sheet material of the instant invention includes a die base, mobile carrier shoes, a plurality of spacer bars, and a pair of rotatable anvils having alternative forming surfaces.
2. Description of the Prior Art
As is generally well-known, press brakes are equipped with a lower press member and an upper press member which are movable relative toward and away from each other. Typically, the lower press member is stationary and the upper press member is reciprocatingly movable toward and away from the lower press member. The upper press member includes commonly a male forming tool (upper die or punch) having a bottom workpiece-deforming surface. The lower press member includes commonly an appropriately shaped lower die having an upper surface vertically aligned with the workpiece-deforming surface of the upper die. When the upper and lower dies are moved toward each other with a workpiece to be formed held over the lower die, the upper die descends into the workpiece and presses it into the lower die so as to deform the workpiece to a desired bent shape. However, it should be understood that the upper press member could be stationary and the lower press member is movable.
It is also generally known that the specific size and shape of the openings used in the lower dies are dependent upon the gauge of the material to be formed as well as the desired shape to be formed. For example, in many cases, the opening in the lower die is similar to the shape of the desired finished bend in the formed material. These openings in the lower dies must have the correct distance across the forming points (contact-forming surfaces) and have a sufficient depth therein so as to allow the required penetration of the material being formed into the lower dies and down to the point for achieving the desired angle of bend in the material.
Further, the side surfaces and the bottom surface of the lower dies must have sufficient strength for withstanding the pressure transferred from the material being formed so as to prevent their flexing and/or splitting. The upper two points (inside edges) of the lower die are the only points of contact or forming surfaces since the material being formed never actually engages with the bottommost area of the lower die. This type of bending operation is sometimes referred to as an “air” bend or “air forming” method. The finished shape of the material is determined by the actual shape of the upper die (punch) and the depth of penetration of the material being formed into the lower die, as the material will then spring back to its finished shape.
One of the major problems encountered heretofore with the prior art press brake dies arises from the fact that it is often necessary to interchange upper and lower dies having different radius of curvatures and different distances therebetween in order to be able to bend and form the material into a desired configuration. While the upper die (punch) may be used for several bending operations for different gauges of materials, this is generally not the case with respect to the lower die having a single-forming capability. Specifically, each gauge or shape of material being formed requires in many cases a separate and different appropriately-sized lower die to be substituted. Since these lower dies are manufactured conventionally from hard tool steel or similar material, they are generally quite large and heavy and are expensive to machine. Thus, these large and heavy lower dies must be unbolted and removed from the lower press member and new lower dies must be installed into the lower press member and then re-bolted. This operation is a considerable hindrance to the metal-forming industry in general since it causes a significant amount of downtime and expensive labor cost in exchanging of the lower dies to and from the press brakes due to their size and weight.
Another associated problem is that these lower dies require storage space for the ones not currently being used so that they can be re-used for future bending operations. This has resulted in a large number of different lower dies being stored for long periods of time at relatively high cost. In addition, there is suffered the disadvantages of having the unnecessary expense in the number of lower dies required to be purchased and of potential business opportunities being lost due to the unavailability of the appropriate lower die.
Accordingly, there exists a need for solving the above-mentioned problems of the prior art press brake dies. It therefore would be desirable to provide a method and apparatus for enhancing the capability of the lower dies in which performance of multiple forming operations with different gauges of sheet material can be achieved without the need of changing to completely different lower dies. It would also be expedient that the apparatus used in press brakes include a multi-form die base with rotatable anvils having alternative forming surfaces. The anvils are significantly smaller and lighter than the conventional lower dies and thus can be removed and installed in substantially less time.
A prior art search directed to the subject matter of this application in the U.S. Patent and Trademark Office revealed the following Letters Patent and application:                U.S. Pat. No. 3,975,721        U.S. Pat. No. 4,403,495        U.S. Pat. No. 4,774,994        U.S. Pat. No. 4,967,585        U.S. Pat. No. 5,116,450        U.S. Pat. No. 5,253,502        U.S. Pat. No. 6,178,799        
In addition to the above issued prior art patents, there were also found published patent application No. 2001/0009106 to Gerritsen on published on Jul. 26, 2001 and published application No. 2003/0033846 to Runk et al. published on Feb. 20, 2003.
In U.S. Pat. No. 6,178,799 to Miller et al. issued on Jan. 30, 2001, there is disclosed a forming press for shaping angle-section workpieces which includes an upper die shoe and a lower die shoe. The upper die shoe has affixed to it a pair of guides and a forming die secured therebetween by sliding the forming die between the guides so that the keys ride in the keyways. The lower die shoe includes a pair of cam blocks and a pair of main body members disposed movably between the cam blocks. The horizontal portions of the main body members support a pair of spacers. Further, the lower die shoe includes a pair of forming die inserts secured to the spacers by keys riding in the keyways.
In U.S. Pat. No. 5,116,450 to Spoo et al. issued on May 26, 1992, there is taught a single die in which includes a mold base section and a mold insert section. The mold insert section is received in a channel portion so as to be removably connected to the mold base section by means of bolts and threaded holes. The die further includes a mold base section and a mold insert section which is received in a channel portion so as to be removably connected to the mold base section by means of bolts and threaded holes. A pair of clamp plates is provided for clamping the die therebetween. The mold insert sections can be disconnected from their corresponding mold base sections by removing the bolts. Then, new mold insert sections defining a different shaped or sized mold cavity can be connected to the respective mold base sections.
In U.S. Pat. No. 4,967,585 to Grimaldo issued on Nov. 6, 1990, there is taught a bending die and ram assembly for use in a tube bending machine which includes a bending die having a convexly curved die face for bending engagement with a metal tube supported by a pair of backshoe dies mounted on an outwardly pivoting pair of back gates. The ram assembly utilizes retractor hooks which cooperate with lugs projecting from the underside of the bending die to permit the die to be attached and detached from the ram assembly in a drop-in, lift-out manner without tools. As a result, multiple bending dies of different sizes can be interchanged without requiring tools to the front of the pusher block.
In U.S. Pat. No. 3,965,721 to Roch issued on Jun. 29, 1976, there is disclosed a die holder frame which is received in a die bed of a press brake. A die holder bar is mounted to the frame and is supported on a plurality of adjustable wedges. The forming die is mounted in the die holder bar. The wedges are individually adjustable to provide a crown along the length of the die holder bar and are adjustable as a group to provide various desired heights of the die bar holder.
The remaining patents, listed above but not specifically discussed, are deemed to be only of general interest and show the state of the art in forming press apparatuses for bending and forming of metal workpieces utilizing a first forming die and a second forming die being movable toward and away from the first forming die.
None of the prior art discussed above disclosed an apparatus for bending and forming sheet material like that of the present invention which includes a die base, mobile carrier shoes, a plurality of spacer bars, and a pair of rotatable anvils having alternative forming surfaces.